الفهرس 
Water-Related DiseasesOnly 14 pages are availabe for public view
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Abstract
Water is very important to human beings. Although human life can exist for many days without food, the absence of water for only a few days has fatal consequences.
The number of different types of pathogens that can be present in water as a result of contamination with human or animal feces is very large and it is not possible to test water samples for each specific pathogen. Therefore, scientists and public health officials typically choose to monitor non pathogenic bacteria that are usually associated with pathogens transmitted by fecal contamination; but are more easily sampled and measured. These associated bacteria are called indicator organisms.
A wide variety of commercial water treatment systems are available for application to treat very small quantities, such as for individual homes or taps. These can treat virtually any water quality problem. Costs are dependent upon many factors. It is important to have a good understanding of the specific water quality problems before selecting water treatment system. It is also important that products be tested and approved by a qualified independent certification organization to have confidence that the device will indeed perform as the vendor claims.
The present study aimed to assess the quality of drinking water in some household water filter systems in Benghazi city.
The study was carried out during 11 months ,from the beginning of March 2008 till the end of January 2009, on a total of 600 water samples (300 tap water samples and 300 filter water devices samples) . These samples were collected monthly.
Tap water samples:
A total of 300 water samples were collected from 21 various areas in Benghazi city (130 samples from DS and 170 samples from tanks).
Filter water devices:
1) Charcoal filter samples
A total of 150 water samples were collected from 14 various areas in Benghazi city.
2) RO filter system samples
A total of 150 water samples were collected from 16 various areas in Benghazi city.
Water samples were aseptically collected in 500 ml sterile bottles. These bottles contained sodium thiosulphate for all water samples .
The water samples were directly transferred to the laboratory and examined within 1-6 hours of collection. Each sample was vigorously shaken and subjected to bacteriological, physical and chemical examination.
Bacteriological examination:
1) Enumeration of HPC using standard pour plate method.
2) Enumeration of TC by two methods MTF and MF.
3) Enumeration of TTC, FS, P. aeruginosa by MF.
The results of this study can be summarized as follows:
1) According to Libyan guidelines, out of 600 examined drinking water samples 76.8% were acceptable.
2) The highest percentage of acceptable samples was revealed from RO system (90.7%), followed by charcoal filter (83.3%), tap water DS (82.3%), and only 54.7% from tap water tanks.
3) The highest percentages of TC, TTC were isolated from tap water tanks (18.2% and 4.1%) respectively, followed by tap water DS (9.2% and 3.1%) respectively.
4) No FS were isolated from tap water or filter devices samples.
5) P. aeruginosa was isolated from filter water devices morning samples only (one sample from charcoal filter and three samples from RO filter system).
6) The highest frequency of isolation of (TC, and TTC) and P. aeruginosa) and the highest mean counts of HPC were revealed from the morning samples.
7) Tap water samples gave a lower percentage of acceptable samples than the RO and charcoal water devices, (65.3% to 90.7 %) and (68.0 to 83.3 %) respectively.
8) RO system brand A was the best brand as regards the bacteriological quality and its compliance with the Libyan standards for drinking water showing acceptable samples 98.2%, followed by RO system brands B and C; (93.3 %) and (80.0%) respectively.
9) Charcoal filter brand A was the best brand as regards the bacteriological quality and its compliance with the Libyan standards for drinking water showing acceptable samples 98.0%, followed by charcoal filter brands B and C; (92.0 % and 60.0% ) respectively.
10) The highest percentages of TC, TTC, P. aeruginosa and HPC were recorded from filter water devices samples of installment duration above 12 months. No indicator organisms were revealed from water samples of RO filter systems installed for less than 12 months with the exception of only one unaccepted sample for TC.
11) Water samples of charcoal filters installed for 12-18 months revealed indicator organisms as TC 13(17.3%), TTC 5(6.7%) and P. aeruginosa one(1.3%).
12) TC were isolated from RO system and charcoal filter water samples when membranes were not changed according to manufacturer’s instructions.
13) The percentage of acceptable tap water and RO filter water samples from Al Kaish region ,Al Rwaysat region ,and Al Sabry region were (100%) each, followed by Al Lithy egion (90.0%).
14) The percentage of acceptable tap water and charcoal filter water samples from Al Fawehat region , Al Kawarsha region , Al Lithy region , Al Rwaysat region, Hay Al Dolar region, Hay Al Salam region and Sidi Younis were (100%) each, followed by Al Sabry region (91.0% ).
15) The highest mean counts for HPC were at Al Wehaishy region (83.47 cfu/ml) followed by Al Salmany (67.27cfu/ml).
16) The highest mean counts of HPC were revealed from tap water tanks (61.2 cfu/ml), followed by tap water DS (24.6 cfu/ml) , charcoal filter (20.4 cfu/ml) and only (18.9 cfu/ml ) from RO system.
17) The highest mean count for HPC in tap water was from samples collected in spring (95.73 cfu/ml) followed by (70.27 cfu/ml) in summer.
18) An agreement of 88.2 % was found between both methods MF and MTF in detection of TC from the examined water samples.
19) The highest temperature, turbidity, EC, ammonia, nitrite, nitrate and residual chlorine mean values were at Al Wehaishy tap water and filter water devices samples.
20) Four specific samples (3 samples from RO filter system and only one sample from charcoal filter) were negative for all bacteriological parameters before filtration and became significantly positive after filtration.
It can be concluded from this study that:
1. Filtered water samples were found to be superior to tap water samples as regards their bacteriological, physical and chemical aspects.
2. The changing of the membranes of the filter devices according to the manufacturerَs instructions resulted in raised efficiency of filter devices where no indicator organisms were isolated from RO systems with changed membranes.
3. According to the Libyan guidelines, brand A of RO filter system and charcoal filters was the best. While brand C represented the worst brand either RO filter system and charcoal filters.
4. P. aeruginosa is considered as an excellent indicator for the efficiency of the water filters.